1. Field of the Invention
This invention relates to deposition processes, and particularly to processes for depositing on a substrate thin films of materials having areas which are accurately positioned relative to each other.
2. Description of Related Art
In the manufacture of a number of different types of electronic devices, two or more thin films of materials must be deposited on a substrate, for example by vacuum deposition, in such a manner that areas of one of the films are accurately located relative to areas of the other film.
One such device is a flat panel liquid crystal display for a colour television receiver. Such a display comprises two parallel spaced apart transparent plates between which a quantity of liquid crystal material is confined. On the inner surface of one plate are deposited parallel stripes, or alternatively rows and columns of rectangular elemental areas, of red, blue and green dyes, to act as colour filters. Corresponding stripes or areas of transparent electrically-conductive material must be deposited over the dye stripes or areas, and exactly in alignment therewith, to act as electrodes for the liquid crystal cells.
A conventional process for depositing such electrodes comprises depositing a film of the conductive material over the entire display area, depositing a layer of a resist material over the conductive film, masking the resist layer, imaging the resist layer, dissolving away the areas of the resist layer corresponding to the spaces between the dye areas, and etching away the conductive layer corresponding to those spaces.
The remaining areas of the conductive layer must be accurately aligned with the dye stripes or rectangular areas, even though the stripes or areas may be only a few microns wide. This process requires extremely accurate positioning of the mask, which is time-consuming and involves the use of expensive equipment.
In an alternative process, the unwanted portions of the conductive layer between the dye stripes or areas are eroded by means of a laser beam. Again, this requires the use of very accurate and expensive positioning equipment.